Dental articulator

ABSTRACT

A DENTAL ARTICULATOR PROVIDED WITH AN ADJUSTABLE BENNETT MOVEMENT INCLUDES A PAIR OF LONGITUDINALLY SPACED ADJUSTABLE POST-MOUNTED, CONDYLE-DEFINING SPHERICAL BEARINGS. A LONGITUDINAL SHAFT PROVIDED WITH A FORWARDLY PROJECTING MOUNTING MEMBER TERMINATES AT OPPOSITE ENDS IN LONGITUDINALLY ADJUSTABLE YOKES WHICH PIVOTALLY SUPPORT CONDYLE PATH MEMBERS FOR ROCKING ABOUT VERTICAL AXES, THE CONDYLE PATH MEMBERS HAVING HORIZONTAL CONDYLE TRACKS WHICH ENGAGE RESPECTIVE CONDYLES. A BENNETT GUIDE MEMBER ISE ADJUSTABLY MOUNTED ON EACH YOKE FOR LIMITING THE LATERAL EXCURSION OF THE SHAFT RELATIVE TO THE CONDYLES AND SCREWS CARRIED BY THE YOKE IN THE PATH OF THE CONDYLE PATH MEMBERS ADJUSTABLY LIMIT THE ANGULAR ROCKING THEREOF.

Dec. 7, 1971 E. R. GRANGER DENTAL ARTICULATOR Filed Aug. 29, 1969 INVEN OR fqwE TR awA/gdfk UM K ATTORNEY United States Patent 3,624,906 DENTAL ARTICULATOR Ernest R. Granger, Pelham, N.Y. (149 Prospect Ave., Mount Vernon, N.Y. 10550) Filed Aug. 29, 1969, Ser. No. 854,152 Int. Cl. A61c 11/00 US. Cl. 32-32 7 Claims ABSTRACT OF THE DISCLOSURE A dental articulator provided with an adjustable Bennett movement includes a pair of longitudinally spaced adjustable post-mounted, condyle-defining spherical bearings. A longitudinal shaft provided with a forwardly projecting mounting member terminates at opposite ends in longitudinally adjustable yokes which pivotally support condyle path members for rocking about vertical axes, the condyle path members having horizontal condyle tracks which engage respective condyles. A Bennett guide member is adjustably mounted on each yoke for limiting the lateral excursion of the shaft relative to the condyles and screws carried by the yoke in the path of the condyle path members adjustably limit the angular rocking thereof.

BACKGROUND OF THE INVENTION The present invention relates generally to an improved apparatus for reconstructive dentistry and it relates particularly to an improved dentalarticulator.

A dental articulator is a mechanical instrument employed to reproduce movements of the lower jaw, or mandible. The upper jaw, the maxilla, is a part of the skull. The mandible is connected to the skull by two joints, one on each side of the head, in front of the ear, called the temporomandibular joint. The relation of the mandible to the maxilla at any particular moment is determined by the temporomandibular joints.

Each temporomandibular joint is divided into two vertically separated compartments by a fibrocartilaginous disc. The disc is interposed between the condyle of the mandible and the eminentia articularis of the temporal bone which defines the path of the condyle and, therefore, the mandible, in the movements of the mandible as the disc slides around the eminentia.

In simple opening and closing movements of the mandible, the condyle rotates on the undersurface of the disc around an axis, referred to as the hinge axis. The simplest form of articulator, the plain line articulator, reproduces only this opening and closing movement, with or without an axis.

In movement of the mandible during mastication, the opening and closing movement thereof brought about by the rotation of the condyle on the undersurface around the hinge axis is always accompanied by a simultaneous gliding of the disc on the eminentia. As the condyle is rotating on the disc it moves with the disc, so that mastication occurs on a closing rotation of the condyle as it is moving around the eminentia.

In a protrusive movement of the mandible, as when incising food, both discs and condyles move forward around the eminentia to bring the teeth forward so that the incisors can cut through the food. The disc and condyle are pulled forward on both sides of the head by the external pterygoid muscle, and held forward as the mandible closes around the hinge axis.

In mastication, the mandible moves to the side on which chewing is taking place, the working side, in a path which is referred to as a lateral excursion of the mandible, the side which is not chewing being called the "ice balancing side. In this lateral excursion, the condyle on the working side rotates while the condyle on the balancing side glides down and forward around the eminentia. The balancing condyle must now follow a different path in lateral excursion that it did in a protrusive movement when both condyles went forward. It must not only move down and forward but also must move medially along a path determined by the rotation of the working condyle. In this lateral excursion the condyles not only open around the hinge axis, but also rotate around another vertical axis called the center of rotation.

In lateral excursion, the chewing movement, the working condyle does not simply rotate around a fixed center of rotation because, as the mandible opens and moves to one side to close in the bolus of food, the working condyle and its center of rotation move across the posterior slope of the eminentia and there is a bodily shift of the mandible to the chewing side. This side shift is called the Bennett movement. As the working condyle moves laterally in the Bennett movement, it also moves forward or backward, and upward or downward, depending upon the anatomy of the individual.

The Bennett movement occurs as a rapid shift during the first phase of the lateral excursion. The balancing condyle moves down and forward a short distance around the eminentia, while it also shifts rapidly medially. This causes the working condyle to move rapidly outward as it is rotating. When the Bennett movement is completed, the Working condyle continues to rotate while the balancing condyle continues on down and forward around the eminentia, following a path which is now a curve around the center of rotation, the curvature of the eminentia, and the opening around the hinge axis. Thus, the lateral chewing path is a compound three-directional movement. The form of the Bennett movement, and the timing of the action varies widely from one individual to another. The timing is the rate at which the balancing condyle moved medially as it was also gliding forward around the eminentia; this is referred to as the immediate side shift.

Articulators which can be adjusted to reproduce all of these movements of the joint are referred to as fully adjustable or anatomical articulators. Up to the present, no articulator has been constructed which can by adjustment reproduce the actual Bennett movement of a given individual; that is, the immediate side shift followed by rotation of the working condyle. After the side shift is completed the balancing condyle must be capable of continuing forward with no more lateral movement than that determined by the center of rotation in the working condyle. That is, the balancing path must change as the condyle is moving forward. Articulators which can be adjusted to reproduce a rapid side shift, cannot reproduce the path of the balancing condyle nor the rotation which follows the side shift.

This has only been possible of achievement on complex articulators by grinding a so-called Bennett guide, from a pantographic tracing of the person. This path had to be constructed and ground at considerable expense to the form of each individual, and in no case has it been possible to reproduce this in the condyle path, as it actually takes place in the skull.

SUMMARY OF THE INVENTION It is a principal object of the present invention to provide an improved apparatus for reconstructive dentistry.

Another object of the present invention is to provide an improved dental articulator.

Still another object of the present invention is to provide an improved dental articulator capable of faithfully reproducing all of the mandible movements.

A further object of the present invention is to provide an improved dental articulator in which a fully adjustable Bennett movement is simply and readily achieved.

Still a further object of the present invention is to provide an improved articulator of the above nature characterized by its versatility, reliability, high order of available accuracy, ruggedness and adaptability.

The above and other objects of the present invention will become apparent from a reading of the following description taken in conjunction with the accompanying drawing.

In a sense, the present invention contemplates the provision of a dental articulator in which a mounting member is supported for movement by a pair of longitudinally spaced couplings, each coupling including a condyle path member engaged by a condyle-defining bearing member, the condyle path member being mounted for rocking about a transverse or vertical axis. Associated with each of the couplings is an adjustable Bennett guide which is preferably curved and extends transversely in the direction of the condyle path to limit the relative side shift of the condyle. Adjustments are also provided for limiting the inward swing of the condyle path members. The Bennett action can be reproduced, by adjustment, in the condyle path itself, just as in the skull, by means of the improved articulator, wherein the condyle path is free to rotate around a vertical or transverse axis as the condyle moves forward, or in lateral excursion. In previously known articulators, the condyle path is locked in a fixed anteroposterior position and cannot change itself to accommodate different excursions. In the device of the present invention, the condyle path on the balancing side can rotate rapidly inwardly to impart a rapid side shift, and then turn to permit the condyle to continue forward by rotation around the working condyle. On the working side, the Bennett movement takes place by sliding of the hinge axis in the condyle to enable the center of rotation to move outward as the mandible is opening around the hinge axis.

The amount of Bennett movement is controlled by the Bennett guide or cam attached to the condyle path member holder. This Bennett guide is advantageously curved, and can be longitudinally adjusted and locked forward or back to control the amount of side shift. As the Bennett guide is adjusted forward, it approaches close to the condyle. As it is slid back it moves further medially from the condyle. So the adjustment of this cam determines the amount of side shift. The condyle cannot slide outwardly on the axis shaft, as it rests against a shoulder on the axis shaft. As the articulator is moved in lateral excursion, the condyle rotates the condyle path on its vertical axis, permitting a rapid bodily shift of the man dible to take place. The condyle continues to move rapidly forwardly and inwardly until it makes contact with the Bennett guide. This now prevents further side shift. The condyle now continues forward in contact with the Bennett guide. This causes the condyle path member to rotate forward as the condyle continues forward.

The timing of the Bennett movement can be adjusted on the balancing side, as in the skull, by means of a timing screw. The timing screw determines the amount the condyle path member can rotate inwardly and, therefore, the distance the balancing condyle will move forward as the side shift occurs before the condyle makes contact with the Bennett guide and stops any further side shift.

On the working side, the direction of the Bennett movement is adjusted by rotating the axis forward or backward. As the working condyle rotates and the axis moves outward, it will go forward or back as determined by the position of the axis shaft.

BRIEF DESORIPTION OF THE DRAWING FIG. 1 is a front perspective view of a dental articulator embodying the present invention;

(FIG. 2 is an enlarged sectional View taken along line 2-2 in FIG. 1;

FIG. 3 is a fragmentary front elevational view of the condyle bearing assembly;

'FIG. 4 is a sectional view taken along line 4-4 in FIG. 2;

FIG. 5 is a View similar to FIG. 4 with the condyle path member shown in a different position; and

FIG. 6 is an exploded perspective view thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, which illustrates a preferred embodiment of the present invention, reference numeral 10 generally designates the improved articular which comprises a base member 11 including a forwardly projecting support arm 12 and a pair of longitudinal mounting bars 13 projecting from the opposite rear sides of support arm 12. A mounting plate 14 is carried atop support arm 12 intermediate the ends thereof and a yoke bracket 15 is separably mounted atop the forward free end of arm 12 and supports a replaceable anterior guide plate 16 for angular adjustment about a longitudinal horizontal axis.

Each mounting bar 13 has a longitudinal track formed in its upper face and is provided with a medial longitudinal slot 17. A pair of longitudinally adjustable posts 18 project upwardly from bars 13, each post being provided a forward shoulder engaging a track delineating lip. tEach past '18 includes a depending tongue which slideably registers with a corresponding slot 17 and is provided with a tapped bore engaged by a thumb screw 19 whereby to permit longitudinal adjustment and locking of posts 18 along bars 13.

Resting atop each post 18 is a horizontal, diametrically grooved disc 20 which is connected by a depending shank with -a lock nut 21 registering with an opening in post 18 to permit angular adjustment and locking of discs 20. A bracket 22 is supported by and adjustable with each disc 20 and includes a horizontal leg 22a engaging the disc groove and a vertical leg 23 eccentric to the axis of disc 20. A horizontal rod or shank 24 projects inwardly from the upper part of each leg 23 and supports at its free end a condyle-defining ball or spherical bearing 26.

A mount bracket 27 is supported by and between condyles 26 by a pair of opposite bearing assemblies 28 which include condyles 26 and provide for the adjustable Bennett movement in accordance with the present invention and all the other jaw simulating movements desired in an articulator. The mount 27 includes a longitudinally or laterally extending clamp 29 having upper and lower jaws 30 provided on their inner faces with confronting longitudinally extending angular grooves. A pair of opposite trunnions 32 have inner sections 33 of square transverse cross section which are engaged by the longitudinal bore in clamp 29 delineated by the confronting grooves and are axially or longitudinally individually adjustable therein and project from the outer ends of clamp 29. A pair of locking screws 34 are associated with clamp 29 for tightening and loosening jaws 30 thereby to permit longitudinal adjustment of trunnions 32 and the locking thereof in preselected positions relative to clamp 29. Each trunnion terminates at its outer end in a stub shaft section 36.

Medically afiixed to upper jaw 30 and projecting forwardly therefrom is a support arm 37 terminating at its forward end in a yoke-defining pair of laterally spaced forwardly projecting arms 38. A mounting plate 39 is releasably secured to the underface of support arm 37 intermediate its ends by a suitable lock screw member 40. An anterior guide pin assembly 41 of known construction is suitably supported at its upper end by and between arms 38 and terminates at its lower end in a follower ball F which slideably engages the upper face of anterior guide plate 16.

Each bearing assembly 28 includes a bracket member or yoke 42 comprising a cylindrical body member having a diametrical slot 45 formed therein to delineate a base or cross web 43 and a pair of vertically spaced outwardly projecting legs 44 having confronting vertically spaced horizontal parallel faces 46. A central axial bore 47 is formed in cross web 43 and is tightly engaged by stub shaft 36 to connect yoke 42 rigidly to a corresponding trunnion 32. Formed in the trailing border of web 43 is a recess 48 having a forwardly outwardly inclined base surface 49 which intersects the outer face of web 43 at a point rearwardly of bore 47 and a rectangular groove 50 of lesser width than recess 48 extends medially forwardly from recess 48 diametrically across the inner face of web 43 beyond the forward side of bore 47. The front inner face 51 of web 43 is forwardly inwardly sloped. A tapped bore 52 is formed in recess base 49.

A condyle path member 53 is supported by each yoke for angular or rocking movement about a vertical or transverse axis and includes a vertical plate 54 having arcuate front and rear edges and parallel top and bottom edges. Plate 54 is positioned between yoke arms 44 with its top and bottom edges closely spaced from or in sliding engagement with the confronting yoke arm faces 46. A pair of pivot pins 56 include cylindrical shanks 57 which rotatably engage diametrically aligned radial bores medially formed in yoke arms 44 and terminate at their inner ends in threaded sections 58 which engage corresponding tapped bores 53a in condyle path plate 54 and terminate at their outer ends in enlarged heads. Thus, the condyle path member 53 is rockable or angular movable about a vertically extending axis transverse to the longitudinal axis of trunnions 32 and clamp 29.

A curved transversely extending condyle path-defining slot 59 is formed in plate 54 and is delineated by opposite spaced parallel races 60 of concentric arcuate transverse cross sections with a diameter approximately that of condyle ball 26. A condyle ball 26 registers with each condyle path 59 and slideably engages races 60 so as to be slideable along condyle race 59 and rockable therein. A lug 61 is swingably supported and releasably lockable by a screw 63 at the upper outer end of condyle path 59 releasably to restrict condyle ball 26 against separation from condyle path 59.

In order adjustably to limit the relative lateral or longitudinal movement between condyle ball 26 and yoke 42 and hence of mount 27 there is provided a Bennett cam or guide 64 which is mounted on web 43 inwardly of and along condyle path 59. Bennett guide 64 includes an elongated guide strip 65 which may be planar or curved and which registers with and extends along and beyond groove 50 substantially to the outer edge of web 43. Integrally formed with the trailing part of guide strip 65 and forming an angle therewith is an enlarged rectangular base plate 66 which engages inclined recess base '49. A lock screw 67 registers with a transversely extending slot 68 in plate 66 and engages tapped bore 52. Thus, by loosening screw 67 and sliding plate 66 along base 49 and then tightening screw 67 the Bennett guide surface 65 may be longitudinally adjusted in yoke 42 thereby to adjust the limits of the lateral excursion of mount 27 independently of the swinging of condyle path member 53 about its vertical axis.

In order adjustably to limit the inward swinging of the forward end of condyle path member 53 a tapped oblique bore is formed in yoke 42 from the upper inner edge thereof forward of bore 47, longitudinally outwardly and radially inwardly through upper yoke leg face 46. A Bennett movement timing screw 69 engages the tapped bore and projects into groove 45 with its end being located in the swinging path of the upper front section of condyle path member 53 so that the inward swinging of the condyle path member front section is adjustably limited by the turning of screw 69. A helical spring 70 is entrapped between the head 71 of screw 69 and yoke 42 to prevent inadvertent turning of screw 69. The inward swinging of the rear section of each condyle path member 53 is adjustably limited by a screw 75 located on the rear upper section of web 43.

The operation and application of the improved dental articular 10 is clear from the above description to one skilled in the art. As previously explained, there are two controls for the Bennett movement, the Bennett guide 64 which determines the amount of side shift, and the timing screw 69 which determines the rate at which the side shift takes place. That is, the timing of the Bennett movement is the rapidity with which the axis on the working side moves outward, as the balancing condyle 26 is moving forward. This is determined by how much forward movement of the balancing condyle takes place as the working condyle completes its outward movement, followed by simple rotation of the working condyle as the balancing condyle continues forward along a different path without further side shift. This is the characteristic Bennett movement, which previously could be reproduced only by grinding a Bennett guide from a pantograph tracing. Thus, with the improved articulator it has been made possible to reproduce this movement by adjustment of the instrument. Extensive studies of masticating tooth contact have shown that this is the most important path of all, to make it possible for teeth to make full functional contact without cusps bumping and colliding. The Bennett guide 64 which determines the amount of side shift, is adjusted by loosening the screw 67, and the Bennett guide 34 is slid forward or backward, to control the amount of side shift. When the cam is locked all the way back in the slot, it allows the maximum range of side shift. When it is locked all the way forward, there I will 'be no side shift. The timing screw 69 determines how much the condyle path can rotate inward as the balancing condyle slides forward. As this screw is turned outward, the condyle path can turn in more sharply at the start of the Bennett movement. That is, the Bennett movement will take place more rapidly, with less forward movement of the balancing condyle. As this screw is turned in more to reduce the rotation of the condyle path, this will reduce the rate of side shift, by causing more forward movement of the balancing condyle as the side shift is taking place. Adjustment of the timing screw 69 will not affect the amount of side shift, unless it is turned so far in that the condyle cannot slide along the Bennett guide. In straight protrusive both condyle paths will be straight. The inward rotation of the condyle path on its axis in lateral excursion creates in the path itself the difference between lateral and protrusive caused by the Bennett movement, and also makes possible the lateral protrusive which is necessary to properly articulate teeth. When setting an articulator with check bites, the position at which the side shift is completed and simple rotation starts is determined by the distance along the Gothic arch at which the check bite was taken. The ideal situation is to take the check bite at the exact point where the side was taken. The ideal situation is to take the check bite at the exact point where the side shift in the joints ends. From a large number of pantograph tracings it has been found that 4 mm. from the apex of the Gothic arch represents the best average. When the Bennett guide 64 has been adjusted to this point, it will automatically produce this timing. Therefore, adjustment of the timing screw is not used with check bites. They would be used only with an actual tracing. If the operator wishes to set the articulator to move only in protrusive, as in setting denture teeth, both timing screws can be turned in to lock the condyle paths straight.

While there has been described and illustrated a preferred embodiment of the present invention, it is apparent that numerous alterations, omissions and additions may be made without department from the spirit thereof.

I claim:

*1. A dental articulator comprising a pair of longitudinally spaced support-defining first members, a mountcarrying second member extending between said first members, and a pair of longitudinally spaced bearing assemblies, each bearing assembly including an element provided with a condyle path and means supporting said condyle path element on one of said first and second members for free rocking about a transverse axis and a condyle element mounted on the other of said first and second members and slideably registering with said condyle path, first means for adjustably limiting the rocking angles of said condyle path elements and second means for adjustably limiting the longitudinal traverse of said second member relative to said first member.

2. The dental articulator of claim 1 comprising a base member, said first members including a pair of posts mounted on said base member and individually longitudinally adjustable thereon, said condyle elements comprising balls mounted atop said posts, said second member comprising a pair of coaxial longitudinal trunnions and means supporting said trunnions for relative longitudinal adjustment thereof, and said condyle path element support means comprising a bracket mounted on a respective trunnion and a transverse pivot member carried by said bracket and engaging a respective condyle path element for rotation about the axis of said pivot member.

3. The dental articulator of claim 2 wherein said sec- 8 ond means comprises a Bennett guide member mounted on said bracket between said condyle ball and a respective trunnion and extending along the direction of said condyle path and having a guide surface confronting said condyle ball whereby to limit the axial excursion of said second member.

4. The dental articulator of claim 3 including means for longitudinally adjusting the position of said Bennett guide member on said bracket.

5. The dental articulator of claim 2 wherein said first means comprises an adjustable stop member located in the swinging path of said condyle path member to limit the swing of said condyle path member about a corresponding transverse axis to an adjustable angle.

6. The dental articulator of claim 2 including means for releasably interlocking said condyles with respective of said condyle path elements.

7. The dental articulator of claim 2 wherein said second member comprises a forwardly projecting arm supported by and between said trunnions and movable therewith a mounting plate releasably supported by said arm.

References Cited UNITED STATES PATENTS 3,350,782 11/1967 Guichet 32-32 3,452,439 7/1969 Lee 3232 3,478,431 11/1969 DePietro 3232 ROBE-RT PESHOCK, Primary Examiner 

